[ECO-4874] Replaced all occurences of checking error message

[maratal]

Replaced all occurences of checking error message instead of error code (or removed where the error code check was already presented) except places where error is locally generated (since it doesn't contain proper error code - 0 usually).

Closes #1946

[lawrence-forooghian]

To check I’ve understood — the error messages that you've removed the checks for are all ones that are generated by the server?

[maratal]

To check I’ve understood — the error messages that you've removed the checks for are all ones that are generated by the server?

correct

[owenpearson]

@maratal found some more here as well:

• https://github.com/ably/ably-cocoa/blob/938ee762bbf3fc65a65bfa23c3f3a769dd6bc9a2/Test/Tests/AuthTests.swift#L4090
• https://github.com/ably/ably-cocoa/blob/938ee762bbf3fc65a65bfa23c3f3a769dd6bc9a2/Test/Tests/AuthTests.swift#L4141
• https://github.com/ably/ably-cocoa/blob/938ee762bbf3fc65a65bfa23c3f3a769dd6bc9a2/Test/Tests/AuthTests.swift#L4261
• https://github.com/ably/ably-cocoa/blob/938ee762bbf3fc65a65bfa23c3f3a769dd6bc9a2/Test/Tests/AuthTests.swift#L4338
• https://github.com/ably/ably-cocoa/blob/938ee762bbf3fc65a65bfa23c3f3a769dd6bc9a2/Test/Tests/RealtimeClientConnectionTests.swift#L2099

[maratal]

Thanks @owenpearson I was looking for error.message but there are also description, localizedDescription, reason.message and error?.message! 🤦‍♂️